# Fluid Mechanics Questions and Answers – Total Pressure & Vertical Plane Surface Submerged in a Liquid

This set of Fluid Mechanics Quiz focuses on “Total Pressure & Vertical Plane Surface Submerged in a Liquid”.

1. Does total pressure takes into the account force exerted by the fluid when it is in the dynamic motion?
a) Yes
b) No
c) Depends on the conditions
d) Depends on the type of Motion

Explanation: Total pressure is defined only for the static fluid at rest. There is no dynamic component as no motion is involved.

2. Can centre of pressure for a vertical plane submerged surface be ever be above centre of Gravity
a) Yes
b) No
c) It can be above in cases where the surface height is very large
d) None of the mentioned

Explanation: Centre of pressure always lies below the centre of gravity. In certain cases it may coincide but it can never be above the centre of gravity.

3. Which principle is used for calculating the centre of pressure?
a) Principle of momentum
b) Principle of conservation of energy
c) Principle of balancing of momentum
d) None of the mentioned

Explanation: We balance the moment in order to calculate the position of centre of pressure.

4. In a vertically submerged plane surface, pressure at evbery point remains same
a) True
b) False

Explanation: Pressure at every point is different as the depth of different point from is different.

5. The magnitude of total pressure and centre of pressure is independent on the shape of the submerged plane surface.
a) True
b) False

Explanation: For differently shaped surfaces, the area and hence position of centroid will be different. Hence, the magnitude of total pressure and centre of pressure is dependent on the shape of the submerged plane surface.

6. What is the variation of total pressure with depth for any submerged surface if we neglect variation in the density?
a) Linear
b) Parabolic
c) Curvilinear
d) Logarithmic

Explanation: Total pressure is given by,
F=w*a*y
hence, F ∝ y i.e linear relation.

7. A pipe line which is 6 m in diameter contains a gate valve. The pressure at the centre of the pipe is 25 N/cm2. If the pipe is filled with specific gravity 0.8, find the force exerted by the oil upon the gate.
a) 7.06 MN
b) 14.12 MN
c) 3.53 MN
d) 28.24 MN

Explanation: ĥ=p/ρg
=250000/9.81*800
=31.855 m
F=wAĥ
=9.81*800*9*π*31.855
=7.06 MN.

8. Determine the centre of pressure on an isosceles triangle plate of base 6m and altitude 6m when it is immersed vertically in an oil of specific gravity 0.75. The base of the plate coincides with the free surface of oil.
a) 6 m
b) 3 m
c) 9 m
d) 12 m

Explanation: ŷ=I/Aĥ + ĥ
I=bh³/36
ŷ=36*2/18 + 2
=3 m.

9. A tank contains water upto a height of 0.5 m above the base. An immiscible liquid of specific gravity 0.75 is filled on the top of water upto 1.5 m height. Calculate total pressure on side of the tank.
a) 17780.61 N/m2
b) 35561.22 N/m2
c) 71122.44 N/m2
d) 8890.31 N/m2

Explanation: F = F1 + F2 + F3
F=w*A*ŷ
F= 8277.18+5518.12+3985.31
= 17780.61 N/m2.

10. A circular opening, 6m diameter, in a vertical side of a tank is closed by a disc of 6m diameter which can rotate about a horizontal diameter. Calculate the force on the disc. The centre of circular opening is at the depth of 5 m.
a) 1.38 MN
b) 2.76 MN
c) 5.54 MN
d) 7.85 MN

Explanation: F=w*A*ŷ
=9.81*1000*3.142*32*5
=1.38 MN.

Sanfoundry Global Education & Learning Series – Fluid Mechanics.

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